Bi-specific antigen binding polypeptides, such as antibodies and antibody-like molecules, hold great promise as therapeutics due their ability to target multiple antigens simultaneously. However, manufacturing of these molecules is a challenge. In the case of bi-specific antibodies, mis-pairing in both heavy and light chains often occurs during production, which reduces the yield of the bi-specific antibodies and makes purification challenging.
To overcome the problems associated with manufacturing of bi-specific antibodies, complex engineering in the antibody constant or variable regions has been attempted. For example, bi-specific antibodies have been generated in which the VH and VL of the individual antibodies are genetically fused via a linker (see e.g., US2010/0254989A1). In another approach individual antibodies were produced with mutations in the Fc in residues of the human IgG4 responsible for Fab exchange (see e.g., Van der Neut at al., Science (2007) 317: 1554). In yet another approach, mouse quadromas were employed for generating bi-specific antibodies. In this approach, the mouse and rat antibodies predominantly form the original VH/VL pairings and the bi-specific antibody consists of the rat and mouse Fc (see e.g., Lindhofer et al., J Immunol. (1995) 155: 1246-1252). Finally, bi-specific antibodies have been generated that use a single, common light chain that does not contribute to antigen binding (see e.g., Merchant et al., Nature Biotechnology (1998) 16: 677-681). However, in spite of these extensive antibody engineering efforts, bi-specific antibodies continue to suffer from poor stability and low functional expression yields.
Accordingly, there is a need in the art for novel antigen-binding polypeptides that are highly expressed and easily purified.